I underwent down s syndrome risk screening test

I underwent down s syndrome risk screening test in 13th week of pregnancy last week. The results are as under: Free beta HCG:91.6 CORR.MOM for Free B-HCG: 2.58 PAPP-A : 10.8 CORR.MOM for PAPP-A: 4.87 Risk of DOWNS (Trisomy 21) : 1:1716 Risk for Trisomy 18: 1:10000 Risk for Trisomy 21 screening (double) : negative Trisomy screening 18 (double): negative My doctor sys that reports are alright bcos mainly two things are seen in this test: Risk for Trisomy 21 screening (double) and Trisomy screening 18 (double) and both are negative. however, acc to normal ranges of free beta HCG (41.02) and PAPP-A (4.25), my results of both are high. but my doctor is not concerned about them. But i am really worried. What could be the reason for high values of these two?